"It has been a good year and I ended the year with another good tournament and won a silver. I will look to play next year with the same confidence and hope to go further," Sindhu said after the match.
The 22-year-old Indian came agonisingly close to clinching the title before finishing runner-up once again in her third major tournament, following last year's Rio Olympics and this year's Glasgow World Championship.
In scenes similar to the World Championship final in August, the summit clash here went down to the wire as the duo engaged in a battle of attrition but in the end it was Yamaguchi who showed better nerves.
"I was not thinking about the longest match but then after the match, it left me with a bad feeling that it was just like the match against Okuhara," said Sindhu, who had finished as runner-up at Hong Kong Open as well in November.
"Yamaguchi's style was more of rally and I was prepared for it. I knew it would be a long match."
Playing her fourth final of the season, Sindhu logged the first point with a magnificent down the line smash. However, a couple of unforced errors and a wrong judgement at the baseline allowed Yamaguchi to make it 3-2.
A lucky net chord gave another point to the Japanese. However, Sindhu unleashed a superb cross court smash to draw parity at 5-5.
The Indian went wide next and another lucky net chord saw Yamaguchi open a 7-5 lead. The Japanese produced another cross court return to gain another point before Sindhu grabbed six straight points to enter the break with a three point advantage.
After the interval, Sindhu moved to 13-8. Yamaguchi grabbed three points, which included a successful video referral, to narrow the lead to 11-14. With the racquet then slipping out of Sindhu's hand and she finding the net, Yamaguchi breathed down her neck at 13-14.
The Japanese, however, hit wide next and Sindhu unleashed two sensational returns, including a quick return on serve, to once again open up a five-point cushion. The Indian finally earned seven game point opportunities with a quick smash near the court. Yamaguchi saved two before Sindhu pocketed the game with a cross court smash.
In second game, Sindhu came out firing on all cylinders as she zoomed to a 5-0 lead. However, the Indian was called for a service fault and she ended up giving another point to her rival, before a wide shot from the Japanese took her to 6 -2.
A couple of unforced errors by Sindhu allowed Yamaguchi to narrow the gap to 7-8 as she set up the next point superbly and closed it with a body smash to draw parity at 8-8. The Japanese then opened up a 10-8 lead after winning another rally before entering the break with a two-point advantage.
Sindhu missed the line twice to allow Yamaguchi lead 13- 10. The Japanese consolidated on the lead to swell to 15-11. The Indian seemed slightly exhausted and ended up committing unforced errors. It helped Yamaguchi to grab the second game and roar back into the contest.
In the decider, Sindhu opened up a 4-0 lead early on, which included winning an engrossing rally comprising 51 shots. However, Yamaguchi once again clawed her way back to 5 -5 with a body smash and an onrushing return at the backline.
Sindhu again eked out a 8-6 lead with a return on her rival's forehand. Yamaguchi too missed the line again as the Indian led 9-7. A backhand tap near the net gave another point to Sindhu, who entered the interval with a three-point advantage after Yamaguchi sent another to the net.
After the change of ends, Yamaguchi narrowed the deficit to 10-11 before Sindhu grabbed a point after being goaded by an animated India coach Pullela Gopichand from the sidelines.
At 13-12, Sindhu missed the line again after another rally to allow Yamaguchi draw parity. What ensued next was yet another engrossing rally where the Indian returned two smashes before leaving her opponent sprawling on the court.
Yamaguchi grabbed two quick points after Sindhu hit wide twice but the Indian then unleashed a jump cross court smash to again make it 15-15.
Sindhu mishit again and then Yamaguchi pushed the shuttle away at the back as the lead exchanged hands again.
A cross court return on the line earned Sindhu a point and she drew level when Yamaguchi's miscued drop shot went to the net. Sindhu produced a precise cross court smash but Yamaguchi unleashed a prompt return to move to 19-18.
A couple of shots on her rival's backhand helped Sindhu claw back again at 19-19 but the Indian found the net next to hand over the championship point to Yamaguchi, who sealed it when the Indian's return got buried at the net.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)